The failure of cardiovascular system to maintain adequate organ perfusion pressure causes inadequate oxygen delivery resulting in tissue hypoxia, lactic acidosis and end organ damage. Inotropes affect the force of myocardial contraction. A positive inotrope will increase myocardial contractility. Vasopressors cause vasoconstriction of blood vessels (most act by α1 receptor activation) and therefore increase mean arterial blood pressure (MAP) and systemic vascular resistance (SVR). Vasoactive drugs are used to support tissue perfusion and hence oxygenation. Vasoactive drugs act on various receptors in the body to produce their effects. Treatment with vasoactive drugs should be considered, if optimization of oxygenation, ventilation and adequate fluid resuscitation fail to restore cardiac output. Therapy may need to be started with minute-by-minute assessment of the patient's response. The response to vasoactive drugs is often unpredictable and dependent on the cause of shock and baseline circulation.